The United States is easily the most militarily powerful country in the history of the world. But it remains baffled about what to actually do on the world stage.

It should be blindingly obvious, but a rational nation-state should develop broad strategies and then implement narrower tactics designed to achieve them. This is especially true, or should be, in the case of the most powerful states — those capable of projecting power beyond their own regions, and in the case of the United States, to every corner of the planet. Countries need long-term goals to guide their actions. Otherwise they end up stumbling around the globe, haphazardly crashing into conflicts seemingly at random — which is exactly what the U.S. has been doing as it pursues a series of disconnected tactics without a coherent overarching strategy to give them direction.

Consider the spectacle of America's contrasting approaches to North Korea (sticks then, carrots now) and Iran (carrots then, sticks now). The overarching strategy seems like it ought to be clear enough: The Trump administration's National Security Strategy, like all such statements since the heyday of so-called "unipolar" moment of uncontested American hegemony in the early 1990s, declares that the goal of U.S. foreign policy is to preserve American global primacy. And so with North Korea and Iran, the Trump administration wants to prevent potentially dangerous rogue states from developing nuclear weapons that could threaten America and its allies.

But the tactics employed to achieve this goal are dumbfoundingly different in each case. Why is Trump scrapping a hard line with North Korea and offering Kim Jong Un legitimacy while threatening to replace Barack Obama's rapprochement with Iran with harsh new punishments? America seems lost and confused in its tactics.

Some of this is obviously just about the impulsiveness and utter lack of knowledge that America's 45th president so routinely displays. But there's a deeper reason why America is so flustered on the world stage: There's a fundamental contradiction at the heart of our strategy.

America doesn't just want to maintain its own primacy. It also wants to foster and spread the liberal international order. And these two goals sometimes do not align.

As Christopher Preble recently argued in a powerful and important op-ed for The New York Times, by fostering the liberal international order, the U.S. "helped to create the conditions that allowed other countries to prosper and grow" into rival powers. If we want to defend the liberal international order, we will need to care less about primacy. On the other hand, if we want to maintain primacy, we will need to care less about spreading liberal democracy around the globe.

You can see this tension playing out when it comes to North Korea and China, the latter of which has risen to the status of a regional and potentially global rival. If our central strategic goal is to maintain our primacy and thwart China's rise, then we should be doing everything in our power to ensure that we remain close allies with South Korea and continue to maintain a large military presence on its territory. That means we should not be overly encouraging of reconciliation between the North and South, since as my colleague Noah Millman notes, any permanent resolution to the conflict on the peninsula would likely create distance between Washington and Seoul, which could only benefit China.

But of course, the liberal internationalist ideal points in the opposite direction — toward the imperative to work for the peaceful coexistence of nations. From that standpoint, we should be doing everything to increase the likelihood of reconciliation on the peninsula without regard for its likely effects on the relative power of the U.S. and China.

Then there is the additional consideration that liberal internationalism also holds that enduring peace can be possible only between free and democratic governments, which means that the prospects of a just order on the Korean peninsula will be impossible so long as the North remains a totalitarian dictatorship.

Is it any wonder that America's approach to North Korea has seemed so frenzied, directionless, and contradictory — with Trump threatening to rain "fire and fury" on Pyongyang and then calling its murderous leader "very honorable?" America's leaders don't even agree on what strategy they're trying to implement.

Such moral and strategic conflicts confront the United States across the globe. So what to do?

One option is to remain on our present course while trying as best we can to untangle the knots, one at a time. But another, wiser path may be to follow Preble's suggestion and begin to realize that our national interests aren't always advanced by seeking to maintain an impossible primacy. Rather than consistently (and futilely) pursuing permanent international preeminence or the continual expansion of the liberal international order to every corner of the globe, it may be better to begin thinking soberly and strategically about how best to manage the relative decline of America's power.

The unipolar moment of the early 1990s has given way to what is likely to be a more enduring multipolar era. We can either face this reality and try to adapt — or else deny it and flail about in confusion.